Code:

 
 
y_background = (256-scroll_reg)%256;

slScrPosNbg1(toFIXED(-220), toFIXED(-(background_y >> 2)));

Code:

 
 
unsigned Z80_RDMEM(dword A)

{

// The basic goal here was to convert from a chain of if/elseif

// statements to a switch construct. The idea is based on the

// fact that all numbers from 0x7800 to 0x7BFF start with 010010,

// while all numbers from 7000 to 73FF start with 010000. The sync

// code is unchanged.

switch(A & 0xFC00)

{

case 0x78:

 if(DipSwitchSYNC == 1)

  {

  VideoDraw();

  DipSwitchSYNC = 0;

  slSynch();

  return 128;

  }

 else return 0;

// My implementation of the control bit mangling is completely

// independent of the overall if/elseif to switch conversion. Feel

// free to use the code that was here before - after all, this is

// untested. It's also a bit hairy, maybe it could be made into a

// macro or something... or maybe I'm just crazy.

case 0x70:

 hexdata |= (Smpc_Peripheral[0].data & PER_DGT_TR) >> 7; // Right Shift = Coin 1

 hexdata |= (Smpc_Peripheral[0].data & PER_DGT_ST) >> 9; // Start Button = 1P Start

 hexdata |= (Smpc_Peripheral[0].data & PER_DGT_TC) >> 5; // C Button = Fire

 hexdata |= (Smpc_Peripheral[0].data & PER_DGT_KR) >> 10; // D-Right = Right

 hexdata |= (Smpc_Peripheral[0].data & PER_DGT_KL) >> 8; // D-Left= Left

 hexdata |= (Smpc_Peripheral[0].data & PER_DGT_TB) >> 1; // B Button = Shield

 hexdata |= 0x0C; // Unused bits

 return hexdata;

default:

// The RAM/ROM read had a call to print a warning, but it was after

// a return, so I don't think it ever executed...

 return RAM[A];

} // switch(A & 0xFC00)